1. Field of the Invention
The present invention relates generally to Data Link Layer (DLL) protocols, and more particularly to a DLL protocol for direct support of network layer protocol data services, i.e. the Internet Protocol (IP), for the Universal Mobile Telecommunications System (UMTS).
1. Description of the Related Art
Layered architecture is a form of hierarchical modularity used in data network design. All major emerging communication network technologies rest on the Open System Interconnections (OSI) layer architecture of the International Organization for Standardization (ISO), illustrated in FIG. 1. In this architecture, a layer performs a category of functions or services. The OSI model defines a Physical Layer (Layer 1) which specifies the standards for the transmission medium, a Data Link Layer (Layer 2), a Network Layer (Layer 3), a Transport Layer (Layer 4) and Application Layers (Layers 5 to 7).
Data Link Control protocols are used to mitigate the effects of impairments introduced by the physical transmission medium. A Data Link Control protocol is designed to deal specifically with the types of impairments found on the radio link and comprises mechanisms to deal with errors on the communications link, delays encountered in transmitting information, lost information, bandwidth conservation, and contention resolution.
The third layer is the Network Layer which implements routing and flow control for the network.
The fourth layer, Transport Layer, provides reliable and transparent transfer of data between end points. It also provides end-to-end error recovery and flow control. For the Internet based protocol model, the Transport Control Protocol (TCP) mainly corresponds to the Transport Layer of the OSI model.
Current wireless networks use layer 2-4 protocols designed specifically for the wired networks. However, there are some major differences between the wireless and the wired environment, resulting in important differences in the way these networks operate.
In a wired network the bit error rates are typically on the order of 10xe2x88x929 or better, and errors and packet loss have a tendency to be random. Therefore, the wired transmission medium could be considered essentially error-free and the TCP data packets are lost mainly due to congestion in the intervening routers. Moreover, in a wired system the transmission channel has a constant bandwidth and is symmetrical, which means the characteristics of the channel in one direction can be deduced by looking at the characteristics of the channel in the other direction. Therefore, it is often easier to use a common link control protocols and to solve congestion problems by adding bandwidth.
On the other hand, in a wireless environment, most of these assumptions are no longer valid. The wireless channel is characterized by a high bit error rate. The errors occur in bursts that can affect a number of successive packets. Due to fading, low transmission power available to the User Equipment (UE), or the mobile station, and effects of interference, the radio link is not symmetrical and the bandwidth of a transmission channel rapidly fluctuates over time.
Furthermore, in a wireless environment, the amount of bandwidth available to the system is fixed and scarce. Adding bandwidth to the radio link may be expensive or even impossible due to regulatory constraints.
In addition, the issues in connection with increasing the transmission bandwidth are substantially different in the wireless environment. In a wired environment increasing the throughput is simply a matter of allocating as much bandwidth as possible to the connection. In a wireless environment, part of the bandwidth is used in error correction. More error correction means less payload. However, more error correction increases the probability of correct delivery without retransmissions. Thus, in the wireless environment increasing the end-to-end throughput may be obtained by reducing bandwidth assigned to payload and using the freed bandwidth for error correction.
The Data Link Layer (DLL) protocols available to date for wireless systems do not attempt to be inclusive as complete DLL protocols. Basically, off-the-shelf protocols intended for different media have been adopted for wireless systems. Even though some of those protocols are standardized, they are not very efficient for the wireless system. Also, some of the interactions between the non-wireless protocols and the communication system have caused a lot of complexities. For example, a point to point protocol (PPP) is currently used to conduct part of the functionality needed for the Data Link Layer (DLL). However, such a protocol imposes new limitations over the communication system. Moreover, for the DLL protocol to support the IP quality of service (IPQoS), the PPP encapsulation must be undone and this lowers the throughput.
Accordingly, there is a need for a specialized DLL protocol for a 3G wireless system which can satisfy the demand for advanced multimedia services in a UMTS environment, to support multiple concurrent voice, packet data, and circuit data services, each type of service having different QoS requirements.
It is an object of the present invention to provide a Data Link Layer (DLL) Quality of Service for UMTS which supports the Internet Protocol (IP), and to alleviate totally or in part the drawbacks of the prior art. This novel DLL removes the need for non-wireless data link protocols with their inherent limitations imposed. Furthermore, a Radio Link Control (RLC) sublayer according to the invention is capable of interfacing with the existing non-wireless Data Link Protocols.
It is another object of the present invention to provide a DLL for a wireless communication system, which supports IP Quality of Service (IPQoS) requirements for various advanced multimedia services in the UMTS environment.
According to one aspect of the present invention, there is provided a Data Link Layer (DLL) protocol for direct support of a network layer protocol in the Universal Mobile Telecommunications System (UMTS). The DDL protocol comprises; at a transmitting end of the UMTS, a plurality of Quality of Service (QoS) planes, each of the QoS planes processing a QoS oriented data packet according to a Quality of Service (QoS) requirement, and providing a radio link control (RLC) frame; a subflow processing module for receiving a network layer protocol data packet, converting the network layer protocol data packet into the QoS oriented data packet, and directing the QoS oriented data packet to one of the QoS planes according to QoS information in the network layer protocol data packet; and an interface between a Data Link Layer and a physical layer for receiving the RLC frame and transmitting same to the physical layer.
According to another aspect of the present invention, there is provided a method for direct processing a network layer protocol data packet for transmission over the UMTS wireless communication system. The method comprises the steps of: separating the radio link control layer of the wireless communication system into a plurality of Quality of Service (QoS) planes, each of the QoS planes processing a QoS oriented data packet according to a QoS requirement, and generating a radio link control (RLC) frame; processing the network layer protocol data packet by converting the network layer protocol data packet into the QoS oriented data packet and directing the QoS oriented data packet to one of said QoS planes according to QoS information in the network layer protocol data packet; and forwarding the RLC frame to a physical layer over a transport channel.
Advantageously, the Data Link Layer according to the invention, enables direct support of the IP networking and IP Quality of Service (IP QoS) in the wireless UMTS system by introducing the QoS planes to handle different QoS requirements.
The Data Link Layer according to the present invention removes the need for other non-wireless data link protocols, such as PPP, to connect to the IP.
Other aspects and features of the present invention will become apparent to those skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.